Institute of Information Science
Email Systems
Junk Mail Filters


The email filter system of IIS uses the open source Sendmail+mimedefang+SpamAssassin+greylist, accompanying sophos for email virus scan. Sophos is an anti-virus software purchased by Academia Sinica. The virus pattern file is updated every hour. Since 2007 Sophos is replaced by CLAMAV. SpamAssassin is a junk mail filter developed by apache.org. It gives every mail a weighted score based on the characteristics of mails. If this score exceeds certain threshold, the mail will be treated as junk. Since Feb 2007 GREYLIST is also included for filtering.

Virus Filter
If the system detects virus contained in a mail, a notification will be sent to the designated recipient. The mail will not be sent to the recipient. Currently zip files are not scanned. Please be very carefull on the zipped file, especially if it contains some executables.

The system will discard the attachment of mail if
  • Virus is detected
  • File extension is exe, com, bat, or scr
Spam Filter
The system detects spam based on the following rules. If the mail is not sent in a standard format, it's easy to be detected as spam.
  • The sender is in the blacklist. The blacklist is retrieved from the database on the Internet.
  • The mail is forged to be outlook format.
Currently we add "** IIS-Spam **" in the subject field for the spam without discarding them. If you use email clients, there's a filter function that you can put all these spam to cirtain mailbox. However with IMAP the function is not supported by OUTLOOK, but is supported by NETSCAPE and MOZILLA.
Other Filter
Emails have any the following property will not be sent by the mail server
  • From is forged to be an IIS address
  • To is forged to be an IIS address
  • Recipient is all-users or researchers, but the sender is not from IIS
If other research groups would like to reject all the mails coming from non-IIS address, please contact the computer center.
User-Defined Rules

Users can set up their own rules by logging to https://iiswww.iis.sinica.edu.tw/CCS/mailfilter/saSetup.php
    • Weighted score
      The system computes a weight score for each mail. Users can set the threshold for rejecting the mails. For example:

      -
      6.9
      Accept
      Accept the mails with score < 6.9
      6.9
      15
      Accept but add the subject with
      **Spam**
      6.9 <= score < 15 will be accepted but marked with **Spam**
      15
      -
      Reject

      Reject the mails with score >=15
    The default is to reject all mails with score larger than 6.9.
    • White List From
      Mails coming from the white list will always be accepted.
      For example:
      feng@iis.sinica.edu.tw (certain address)
      *@iis.sinica.edu.tw (certain domain)
      *.sinica.edu.tw (certain subdomain)

    • Black List From
      Mails coming from the black list will always be rejected.
      The setting is similar to white list.
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